1. Technical Field
This invention relates generally to a mounting system for an electromagnetic apparatus such as an inductor or transformer, and, more particularly, to such a mounting system which further includes a cooling function.
2. Description of the Related Art
The use of an electromagnetic apparatus, such as a transformer or an inductor, in electronic assemblies is common in the automotive industry. The electromagnetic apparatus generally includes a magnetic core and a winding disposed on the core (i.e., one for an inductor, or two windings for a transformer). High-frequency operation of the apparatus generates heat, both within the winding and in the magnetic core itself. As the operating frequency increases, so too does the heat component in the core. To avoid reduced performance, and/or damage, the heat generated in the core must be removed. Heat removal may occur either through transfer from the core surface by convection to the surrounding air or by direct thermal contact with an adjacent solid material (i.e., a heat sink). As to the former mode, it is often undesirable to heat the surrounding air, as this can make the surrounding air too hot for neighboring electrical components. Accordingly, the latter mode of heat transfer (i.e., direct thermal conduction) is often used to remove heat from the core/windings to avoid increasing the surrounding air temperature.
As further background, the heat generated in the windings is generally of higher concern than that in the core material. This is because effective heat transfer across multiple turns of insulated wire is difficult to achieve while maintaining moderate temperature gradients in the wires. That is, layers of electrical insulation and air gaps associated with the turns of wire make conduction of heat across the winding very inefficient. For this reason, it is known to apply potting material to encapsulate the winding to eliminate air gaps and thereby increase the effective thermal conductivity. Heat generated in the winding must also be removed, and is either transferred into the core material, or, into the surrounding air by way of convection. As mentioned above, however, heating of the surrounding air is generally undesirable inasmuch as it increases the surrounding air temperature, perhaps to elevated levels detrimental to surrounding electrical components. Accordingly, in view of e forgoing, there has been much investigation into systems for cooling both magnetic cores and windings.
One approach taken in the art to address some of the foregoing problems involves sandwiching a magnetic core between two sheets of thermally conductive material such as metal, as seen by reference to U.S. Pat. No. 5,210,513 issued to Khan et al., hereby incorporated by reference in its entirety. Khan et al. disclose an electromagnetic apparatus including a magnetic core having at least one winding disposed on a central leg of the core. Khan et al. further disclose a first, generally planar heat sink on one side of the magnetic core, and a second heat sink, also generally planar in shape, on an opposing side of the core. Both heat sinks are attached so as to engage the magnetic core in a sandwich arrangement. However, Khan et al. does not address the problem described above dealing with the removal of heat generated in the windings, and, appears to allow much of the generated heat to be transferred to the surrounding air, which is generally undesirable. Additionally, Khan et al. does not appear to protect against damage to the delicate windings/core material due to vibration or structural shock, particularly shock in the plane of the sandwiching metal sheets. The automotive environment, for example, is characterized by high vibration and/or repeated shock. These factors also require due consideration when evaluating mechanisms for mounting an electromagnetic apparatus destined for such relatively harsh environments. Finally, the system of Khan et al. may not be effective with multiple cores secured by the same metal sheet due to dimensional tolerances.
There is therefore a need for an improved mounting apparatus for an electromagnetic device that minimizes or eliminates one or more of the shortcomings as set forth above.
The mounting apparatus for an electromagnetic device according to the present invention is characterized by the features specified in claim 1.
One advantage of the present invention is that it provides improved thermal conduction from the magnetic core to a heat sink to thereby maintain relatively cooler magnetic cores/windings. In addition, the present invention integrates the function of a vibration resistant mounting system with a thermal cooling system.
A mounting apparatus in accordance with the invention is provided for mounting and cooling an electromagnetic device. The electromagnetic device is of the type having a first winding disposed on a core formed of magnetically-permeable material. The mounting apparatus includes a first heat sink and a second heat sink, characterized in that: one of the first and second heat sinks comprises a mounting cup formed of thermally-conductive material having a cavity configured to receive the electromagnetic device, the mounting cup including a flange portion for attachment to the other one of the first and second heat sinks; and potting material disposed in the cavity of the mounting cup encapsulating portions of the electromagnetic device, wherein the flange includes a passage for routing leads of the first winding out of the cavity.
Other objects, features, and advantages of the present invention will become apparent to one skilled in the art from the following detailed description and accompanying drawings illustrating features of this invention by way of example, but not by way of limitation.